Development of Activity-Based Probes for Imaging ... - ACS Publications

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The Journal of Organic Chemistry

Development of Activity-Based Probes for Imaging Human α-L-Fucosidases in Cells Yu-Ling Hsu,a,‡ Manjula Nandakumar,b,c,‡ Hsin-Yi Lai,a Tzyy-Chao Chou,a Chi-Yuan Chu,a Chun-Hung Lin,a,b,c,* and Lee-Chiang Loa,*

a

Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan. Tel: 886-2-33661669; FAX: 886-2-33668670; E-mail: [email protected]

b

Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan. Tel: 886-2-27890110; Fax: 886-2-26539142; E-mail: [email protected]

c

Chemical Biology and Molecular Biophysics, Taiwan International Graduate Program,

Academia Sinica, No.128, Academia Road Section 2, Nan-Kang, Taipei 11529, Taiwan

(RECEIVED DATE)

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ABSTRACT. We have established a concise synthetic route relying on a key base-promoted epimerization step to synthesize two series of activity-based probes carrying a BODIPY fluorophore for α-L-fucosidase. The resulting probes were evaluated for labeling performance. The one utilizing an o-fluoromethylphenol derivative as the latent trapping unit was successfully applied for the first time to visualize and locate lysosomal α-L-fucosidase activity in human cells.

Keywords Quinone methide, synthesis, BODIPY, lysosomal hydrolase, fluorescence, fucosidase

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α-L-Fucosidase, a member of the family of glycoside hydrolases (GHs), catalyzes the hydrolytic removal of L-fucose residues from glycoconjugates. Its clinical importance is linked to the abnormal level of enzyme activity in several pathological conditions, such as genetic disorder, inflammation,1 carcinoma of stomach, ovary2 and liver,3 cystic fibrosis4 and the infection of Helicobacter pylori.5 For instance, fucosidosis is a lysosomal storage disorder caused by the deficient α-L-fucosidase activity owing to genetic defect. As a consequence, the growing number of clinical findings makes it necessary to study the details of the role and activity of α-L-fucosidases in disease conditions. To date, intracellular detection of fucosidase relies heavily on antibodies raised against the target enzyme.6,7 However, this immunological approach could only reveal the amount of proteins instead of their catalytic activity. We therefore envisioned that the development of an activity-based probe that is capable of indicating the intracellular α-L-fucosidase activity would be a valuable diagnostic tool.

Scheme 1. The general structure of activity-based probes 1a and 1b, and the proposed labeling mechanism. To date, activity-based probes exploiting quinone methide chemistry have been developed for a wide variety of hydrolases, including tyrosine phosphatase,8-10 sulfatase,11,12 and numerous glycosidases (glycoside hydrolases, GHs; EC 3.2.1).13-17 Generally, the probes (1a and 1b)

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comprise three structural components, namely, a recognition unit, a latent trapping unit and a reporter unit (Scheme 1). The latent trapping unit, of which o-fluoromethylphenol (2a) and o-difluoromethylphenol (2b) derivatives are two important representatives, plays a key role in forming a covalent linkage with the target. The covalent bond-forming feature of activity-based probes has been extensively explored for versatile applications, ranging from protein profiling18 to the capture of influenza viruses.19 More recently, we have seen a growing trend to developing probes for intracellular imaging applications.12,14,20 However, most activity-based probes for GHs reported to date are limited to those that have 1,2-trans configuration on the pyranoside ring. Probes for α-L-fucosidase, with their 1,2-cis configuration, represent a highly challenging task. We herein report a concise synthesis and the efficacy of two activity-based probes 5a and 5b carrying a BODIPY fluorescent tag, as shown in Figure 1, for the detection of α-L-fucosidase in human cells.

Figure 1. The structure of activity-based probes 5a and 5b for α-L-fucosidase. Recent progress on glycosylation reactions indicated that a high degree of control of the anomeric configuration could be achieved through manipulations of the participating glycosyl donor, protecting group, solvent, and promoter.21-25 However by adopting these strategies, it also implies that a longer synthetic route would be inevitable which in turn would result in the final products being less accessible for practical applications. We herein employ a straightforward

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approach to develop a concise synthetic route for probes 5a and 5b beginning with the easily accessible peracetylated fucosyl bromide 615 and 2-hydroxy-5-nitrobenzaldehyde 7. It is interesting to note that peracetylated fucopyranoside could couple with a phenol derivative under BF3-mediated condition to give mainly the 1,2-cis product in a moderate yield.15,26 However, we failed to observe the formation of any desired glycosylated product when compound 7 was subjected to this condition. In contrast, 7 reacted smoothly with fucosyl bromide 6 under classical Koenigs–Knorr condition27 to afford glycosylated product 8 in 67% yield (Scheme 2). Although compound 8 is a 1,2-trans product, we discovered that it could undergo base-promoted epimerization26 on treatment with K2CO3 in DMSO in the presence of molecular sieves. The reaction mixture consisted of anomers 8 and 9 with the latter being the dominant form as determined by NMR spectroscopy (8/9 = 29/71). More importantly, the two isomers could be separated by silica gel column chromatography. Compound 9 was thus obtained in 48% yield with concomitant recovery of compound 8 (24%). This was the most critical step in the preparations of probes 5a and 5b as compound 9 is the key intermediate that stands at a branch point of the synthetic route for both probes. For the synthesis of probe 5a, the formyl group of compound 9 was first reduced with NaBH(OAc)3 to give benzylic alcohol 10. The nitro group was then reduced by catalytic hydrogenation. Without further purification, the newly generated arylamine was Boc-protected by treatment with (Boc)2O to give compound 11. The benzylic alcohol of compound 11 was converted to a benzylic fluoride in the presence of DAST in CH2Cl2 to afford compound 12 in

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78% yield. Subsequent treatment with TFA to remove the Boc-protecting group followed by coupling with carboxylic acid 1329 under a standard carbodiimide condition (EDC/HOBt) afforded compound 14a. Compound 14a was deprotected by TFA to remove the Boc group and coupled with the BODIPY fluorophore (BODIPY-OSu, 15)30,31 to give the protected probe precursor 16a. Final deprotection was achieved by treatment with Na2CO3 in MeOH to remove all the acetyl groups which provided probe 5a in high yield (92%).

Scheme 2. Synthesis of probe 5a. For the synthesis of probe 5b, as shown in Scheme 3, the aldehyde of compound 9 was directly converted to a difluoromethyl group under the same fluorination condition as that for compound 11. The nitro group of compound 17 was then reduced by catalytic hydrogenation, followed by amide formation with carboxylic acid 13 under the carbodiimide method to give compound 14b. Compound 14b was then consecutively subjected to the Boc deprotection, amide formation with 6


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BODIPY-OSu 15, and peracetate deprotection as those for probe 5a to smoothly afford probe 5b. Particularly because the difluoromethyl group of compound 17 could survive the catalytic hydrogenation condition, we were able to perform fluorination prior to the hydrogenation. Owing to this advantage, the synthetic route of probe 5b was two steps shorter than that of probe 5a.

Scheme 3. Synthesis of probe 5b. To investigate and compare the labeling efficacy of probes 5a and 5b after enzymatic cleavage, as depicted in the proposed mechanism (Scheme 1), we conducted a simple slot blot analysis11 on a protein extract containing α-L-fucosidase. In brief, a protein extract (40 µg) from E. coli expressing Thermotoga maritima fucosidase (TmFA) was incubated with probes 5a and 5b, respectively, at four different concentrations (5, 10, 20, and 50 µM). After incubation for 1 h at room temperature in the dark, the reaction mixtures were blotted onto PVDF membrane and the resulting membrane was washed three times. The retained fluorescent signals were then visualized using Fujifilm LAS-4000 Image acquisition system (λex = 497 nm, λem = 520 nm). As shown in Figure 2, probe 5a gave clear signals at all four concentrations, displaying an increasing trend in labeling intensity with concentrations. By contrast, probe 5b resulted in negligible signals, producing only a relatively weak signal even at the highest concentration (50 µM). 7



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Interestingly, the different performance of chemical probes caused by the latent trapping unit derived from either a fluoromethylaryl or a difluoromethylaryl group has been observed in other systems as well.12,17,32 Probe 5a was shown to detect the active form of TmFA as low as 120 nM in vitro and was able to distinguish between active enzyme and inactive one (prepared by heating the enzyme at 90 °C for 5 min) (Figure S1a). In addition, the labeling intensity towards TmFA displayed good linear response up to 480 nM (Figure S1b). The slot blot assay of TmFA using 5a also gave comparable results to the conventional fucosidase assay (Figure S2). Probe

50 M

20 M

10 M

5 M

5a 5b

Figure 2. Comparative slot blot analysis of probes 5a and 5b on protein extracts containing T. maritima α-L-fucosidase. The fluorescence signals were visualized with Fujifilm LAS-4000 Image acquisition system (λex = 497 nm, λem = 520 nm). To show the permeability and specificity of 5a in complex systems, we performed confocal imaging in 5a-treated human gastric adenocarcinoma epithelial cells (AGS) and HEK-293T cells. AGS and HEK-293T cells were first incubated with 5a (10 µM). After extensive washes to remove the unreacted probe, the images of confocal fluorescence microscopy were acquired to indicate the probe was cell permeable (Figure 3a, upper panel). To validate the observed signals in cells to be α-L-fucosidase-specific, 5 µM of 1-aminomethyl-1-deoxy-fuconojirimycin (FNJ, a previously reported potent inhibitor)33,34 was added to the cultured AGS or HEK-293T cells prior to the labeling step. The presence of FNJ was able to significantly abolish the signal of 5a (Figure 3a, lower panel), supporting the probe efficacy. Furthermore, to find the subcellular localization of the enzyme, we treated AGS cells with 5a (10 µM), and then with counterstains of a lysosome 8


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marker (lysotracker) and a nucleus marker (Hoechst). The probe signal was found to majorly overlap with that of lysotracker (Figures 3b), indicating that the labeling of 5a was likely corresponding to the lysosomal α-L-fucosidase.

Figure 3. Specificity of probe 5a in cells: (a) Confocal imaging of AGS and HEK-293T cells that were treated with 5a (10 µM) in the presence or absence of FNJ (5 µM). (b) Co-localization of 5a-treated AGS cells with Lysotracker. Hoechst was used to stain the nucleus. In conclusion, we have developed a concise synthetic route to synthesize two series of activity-based probes for detection of α-L-fucosidase, one with a fluoromethylaryl group and the other with a difluoromethylaryl group. The latter probe was successfully applied for the first time to visualize and locate lysosomal α-L-fucosidase activity in human cells. It should also be emphasized that the key base-promoted epimerization step exploited in this study could be further extended to the preparation of probes for other glycosidases, such as α-D-glucosidase and α-D-galactosidase, that require 1,2-cis configuration in the glycosylated products.

Experimental Section:

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General Methods. All reagents and starting materials were obtained from commercial suppliers and were used without further purification. Pyridine, dichloromethane, and acetonitrile were distilled from calcium hydride. Analytical TLC (silica gel, 60 F254) were visualized under UV light or stained with phosphomolybdic acid-ethanol and 5% sulfuric acid in ethanol. Column chromatography was performed with silica gel (230−400 mesh). 1H,

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F and

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C NMR were

recorded in the designated deuterated solvents (CDCl3 or CD3OD). The following abbreviations were used to explain the multiplicities: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, b = broad. Melting points were recorded without correction. (2-Formyl-4-nitrophenyl)-tetra-O-acetyl-β β -L-fucopyranoside (8). To an ice-cooled solution of the glycosyl bromides 6 (941.2 mg, 2.67 mmol) and 2-hydroxy-5-nitrobenzaldehyde 7 (490.8 mg, 2.94 mmol) in 5 mL of anhydrous MeCN was slowly added DIEA (1.3 mL, 8.02 mmol). The reaction mixture was stirred for 24 h under N2 at room temperature, and then it was concentrated under reduced pressure. The residue obtained was dissolved in EtOAc (50 mL) and the solution was washed with 5% citric acid (25 mL x 3), 5% NaHCO3 (25 mL x 3), H2O (25 mL x 3) and brine (25 mL). The organic phase was then dried over anhydrous Na2SO4, filtered and concentrated. Purification by silica gel column chromatography (eluent: 70% hexane/EtOAc) provided the desired glycosidation products as white solids in 67% yield. Rf = 0.38 (hexane/EtOAc = 1/1), mp 156−157 oC. 1H-NMR (CDCl3, 400 MHz): δ 10.33 (s, 1 H), 8.68 (d, J = 2.8 Hz, 1 H), 8.41 (dd, J = 9.1, 2.8 Hz, 1 H), 7.25 (d, J = 9.1 Hz, 1 H), 5.59 (dd, J = 10.5, 7.9 Hz, 1 H), 5.36 (d, J = 3.2 Hz, 1 H), 5.29 (d, J = 7.9 Hz, 1 H), 5.18 (dd, J = 10.5, 3.2 Hz, 1 H),

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4.10 (q, J = 6.3 Hz, 1 H), 2.21 (s, 3 H), 2.05 (s, 3 H), 2.02 (s, 3 H), 1.30 (d, J = 6.3 Hz, 3 H). 13

C-NMR (CDCl3, 100 MHz): δ 187.2 (Al), 170.4 (C=O), 170.1 (C=O), 169.4 (C=O), 162.2 (C),

143.1 (C), 130.2 (CH), 125.6 (C), 124.3 (CH), 115.6 (CH), 98.7 (CH), 70.6 (CH), 70.3 (CH), 69.5 (CH), 68.0 (CH), 20.7 (CH3), 20.6 (CH3), 20.6 (CH3), 16.0 (CH3). IR (KBr): 3340, 1740, 1684, 1530, 1383, 1341, 1236, 1061 cm−1. FAB MS m/z (%) 273.1 (100), 462.2 (M+Na+, 6). HRMS (FAB) calcd for C19H21NNaO11 (M+Na)+ 462.1012, found 462.0992. (2-Formyl-4-nitrophenyl)-tetra-O-acetyl-α-L-fucopyranoside (9). To a mixture of the glycosidation product 8 (1.0 g, 2.3 mmol), trace amount of 3 Å molecular sieve and K2CO3 (3.1 g, 22 mmol) was added dropwise 8 mL of anhydrous DMSO. The reaction mixture was stirred for 48 h at room temperature, diluted with 50 mL of CHCl3, and washed with 5% NaHCO3 (25 mL x 3). The aqueous layers were collected and re-extracted with 25 mL CHCl3, and then the organic phase was combined with previous CHCl3 layer, washed with 5% citric acid (25 mL x 2) and brine (25 mL). The organic phase was then dried over anhydrous Na2SO4, filtered and concentrated. Purification by silica gel column chromatography (eluent: 70% hexane/EtOAc) provided the desired product 9 as pale yellow solid in 48% yield and the recovery yield of compound 8 was 24%. Rf = 0.45 (hexane/EtOAc = 1/1), mp 143−145 oC. 1H-NMR (CDCl3, 400 MHz): δ 10.51 (s, 1 H), 8.71 (d, J = 2.8 Hz, 1 H), 8.41 (dd, J = 9.2, 2.8 Hz, 1 H), 7.41 (d, J = 9.2 Hz, 1 H), 5.92 (d, J = 3.5 Hz, 1 H), 5.51 (dd, J = 11.0, 3.0 Hz, 1 H), 5.40 (d, J = 3.0 Hz, 1 H), 5.36 (dd, J = 11.0, 3.5 Hz, 1 H), 4.25 (q, J = 6.3 Hz, 1 H), 2.20 (s, 3 H), 2.01 (s, 3 H), 2.00 (s, 3 H), 1.18 (d, J = 6.3 Hz, 3 H).

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C-NMR (CDCl3, 100 MHz): δ 186.7 (Al), 170.3 (C=O), 170.2

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(C=O), 169.9 (C=O), 162.6 (C), 142.9 (C), 130.6 (CH), 125.6 (C), 124.4 (CH), 116.1 (CH), 96.3 (CH), 70.2 (CH), 67.5 (CH), 67.3 (CH), 66.8 (CH), 20.7 (CH3), 20.6 (CH3), 20.5 (CH3), 15.8 (CH3). IR (KBr): 2919, 2846, 1746, 1699, 1613, 1587, 1540, 1487, 1381, 1348, 1229, 1076, 1036, 977, 910, 738 cm−1. FAB MS m/z (%) 273.1 (100), 462.2 (M+Na+, 11). HRMS (FAB) calcd for C19H21NNaO11 (M+Na)+ 462.1012, found 462.0992. (2S,3S,4R,5R,6S)− −2− −(2− −(Hydroxymethyl)− −4− −nitrophenoxy)− −6− −methyltetrahydro− −2H− −py ran− −3,4,5− −triyl triacetate (10). To a solution of compound 9 (100 mg, 0.228 mmol) in 2 mL of EtOH was added NaBH(OAc)3 (168.9 mg, 0.797 mmol). The reaction mixture was stirred for 24 h, diluted with 50 mL of EtOAc, and washed with H2O (25 mL x 3) and brine (25 mL). The organic phase was then dried over anhydrous Na2SO4, filtered and concentrated. Purification by silica gel column chromatography (eluent: 70% hexane/EtOAc) provided desired product 10 as a colorless solid in 95% yield. Rf = 0.38 (hexane/EtOAc = 50/50), mp 174−175oC. 1H-NMR (400 MHz, CDCl3): δ 8.18 (d, J = 2.7 Hz, 1 H), 8.05 (dd, J = 9.0, 2.7 Hz, 1 H), 7.16 (d, J = 9.0 Hz, 1 H), 5.75 (d, J = 3.6 Hz, 1 H), 5.45 (dd, J = 10.9, 3.2 Hz, 1 H), 5.32 (d, J = 3.2 Hz, 1 H), 5.31 (dd, J = 10.9, 3.6 Hz, 1 H), 4.80 (d, J = 14.0 Hz, 1 H), 4.66 (d, J = 14.0 Hz, 1 H), 4.20 (q, J = 6.4 Hz, 1 H), 3.06 (s, 1 H), 2.15 (s, 3 H), 2.02 (s, 3 H), 1.97 (s, 3 H), 1.11 (d, J = 6.5 Hz, 3 H). 13C-NMR (100 MHz, CDCl3): δ 170.4 (C=O), 170.1 (C=O), 170.0 (C=O), 158.7 (C), 142.6 (C), 131.6 (C), 124.7 (CH), 123.6 (CH), 113.7 (CH), 95.6 (CH), 70.4 (CH), 67.7 (CH), 67.3 (CH), 66.2 (CH), 59.9 (CH2), 20.5 (CH3), 20.5 (CH3), 20.4 (CH3), 15.7 (CH3). IR (KBr): 3555, 1749, 1519, 1348,

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1232 cm−1. HRMS (ESI-quadrupole) calcd for C21H26NO13 (M+AcOH-H)+ 500.1404, found 500.1414. (2S,3S,4R,5R,6S)− −2− −(4− −(tert− −Butoxycarbonylamino)− −2− −(hydroxymethyl)phenoxy)− −6− −met hyltetrahydro− −2H− −pyran− −3,4,5− −triyl triacetate (11). To a solution of compound 10 (224 mg, 0.509 mmol) in 5 mL EtOAc was added 20% Pd/C catalyst (44.9 mg). The reaction mixture was purged and filled with H2, stirred for 30 min at room temperature.

Thereafter, (Boc)2O (49.9

µL, 0.233 mmol) was added to the reactor and stirred for another 24 h. It was then filtered through a fritted funnel dry packed with Celite and concentrated under reduced pressure. The residue was diluted with 50 mL of EtOAc, and washed with H2O (25 mL x 3) and brine (25 mL). The organic phase was then dried over anhydrous Na2SO4, filtered and concentrated. Purification by silica gel column chromatography (eluent: 70% hexane/EtOAc) provided desired product 11 as a colorless solid in 82% yield. Rf = 0.41 (hexane/EtOAc = 4/6), mp 68−70 oC. 1H−NMR (400 MHz, CDCl3): δ 7.26 (s, 1 H), 7.21 (d, J = 8.8 Hz, 1 H), 7.03 (d, J = 8.8 Hz, 1 H), 6.63 (s, 1 H, NH), 5.54 (d, J = 3.7 Hz, 1 H), 5.45 (dd, J = 10.9, 3.3 Hz, 1 H), 5.33 (d, J = 3.3 Hz, 1 H), 5.31 (dd, J = 10.9, 3.7 Hz, 1 H), 4.76 (d, J = 13.1 Hz, 1 H), 4.47 (d, J = 13.1 Hz, 1 H), 4.28 (q, J = 6.5 Hz, 1 H), 2.92 (s, 1 H), 2.15 (s, 3 H), 2.02 (s, 3 H), 1.97 (s, 3 H), 1.45 (s, 9 H), 1.12 (d, J = 6.5 Hz, 3 H). 13C−NMR (CDCl3, 100 MHz): δ 170.5 (C), 170.1 (C), 169.9 (C), 153.0 (C), 150.7 (C), 133.5 (C), 130.9 (C), 119.7 (CH), 119.3 (CH), 115.4 (CH), 96.2 (CH), 80.4 (C), 70.7 (CH), 68.0 (CH), 67.6 (CH), 65.5 (CH), 61.4 (CH2), 28.2 (CH3), 20.6 (CH3), 20.5

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(CH3), 15.8 (CH3). IR (KBr): 3368, 2978, 2931, 1748, 1534, 1500, 1369, 1224, 1161, 1051 cm−1. HRMS (ESI-quadrupole) calcd for C24H33NNaO11 (M+Na)+ 534.1951, found 534.1940. (2S,3S,4R,5R,6S)− −2− −(4− −(tert− −Butoxycarbonylamino)− −2− −(fluoromethyl)phenoxy)− −6− −meth yltetrahydro− −2H− −pyran− −3,4,5− −triyl triacetate (12). To an ice-cooled solution of compound 11 (47.0 mg, 0.0922 mmol) in 0.5 mL of anhydrous CH2Cl2 was added a solution of DAST (17 µL, 0.138 mmol) in 0.5 mL of anhydrous CH2Cl2. The reaction mixture was allowed to warm to room temperature, and stirred for 2 h under N2. It was then quenched by adding small amount of silica gel and 1 drop of MeOH, filtered and concentrated under reduced pressure. Purification by silica gel column chromatography (eluent: 70% hexane/EtOAc) provided the desired product 12 as a pale yellow oil in 78% yield. Rf = 0.50 (hexane/EtOAc = 4/6). 1H-NMR (400 MHz, CDCl3): δ 7.37 (s, 1 H), 7.26 (d, J = 8.7 Hz, 1 H), 7.04 (d, J = 8.4 Hz, 1 H), 6.60 (s, 1 H), 5.57 (d, J = 3.6 Hz, 1 H), 5.51-5.26 (m, 4 H), 5.23 (dd, J = 10.9, 3.7 Hz, 1 H), 4.26 (q, J = 6.5 Hz, 1 H), 2.15 (s, 3 H), 2.01 (s, 3 H), 1.98 (s, 3 H), 1.46 (s, 9 H), 1.11 (d, J = 6.5 Hz, 3 H).

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C-NMR (100 MHz,

CDCl3): δ 170.5 (C), 170.4 (C), 170.0 (C), 152.9 (C), 150.3 (d, J = 4.3 Hz, C), 133.5 (C), 126.4 (d, J = 16.7 Hz, C), 120.6 (CH), 120.2 (CH), 115.9 (CH), 96.1 (CH), 80.5 (C), 79.7 (d, J = 166.0 Hz, CH2F), 70.8 (CH), 67.9 (CH), 67.7 (CH), 65.4 (CH), 28.2 (CH3), 20.6 (CH3), 20.5 (CH3), 20.5 (CH3), 15.8 (CH3). 19F-NMR (376 MHz, CDCl3): δ -213.3 (t). IR (neat): 3368, 2978, 2931, 1748, 1534, 1500, 1369, 1224, 1161, 1051 cm-1. HRMS (ESI-quadrupole) calcd for C24H32FNNaO10 (M+Na)+ 536.1908, found 536.1919.

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(2S,3S,4R,5R,6S)− −2− −(4− −(2,2− −Dimethyl− −4− −oxo− −3,8,11,14− −tetraoxa− −5− −azahexadecanamido )− −2− −(fluoromethyl)phenoxy)− −6− −methyltetrahydro− −2H− −pyran− −3,4,5− −triyl triacetate (14a). Compound 12 (135 mg, 0.26 mmol) was dissolved in 0.7 mL of 20% TFA/CH2Cl2. The solution was stirred at rt for 1 h. The volatiles were concentrated under reduced pressure and then kept under high vacuum for 3 h to remove the residual TFA. The residue obtained was dissolved in 1.8 mL of CH2Cl2 and the solution was added compound 13 (89.8 mg, 0.266 mmol), HOBt (17.8 mg, 0.132 mmol), DIEA (109 µL, 0.658 mmol) and EDC (100 mg, 0.527 mmol). The reaction mixture was stirred for 24 h, diluted with 50 mL of EtOAc, and washed with 5% citric acid (25 mL x 3), 5% NaHCO3 (25 mL x 3), H2O (25 mL x 3) and brine (25 mL). The organic phase was then dried over anhydrous Na2SO4, filtered and concentrated. Purification by silica gel column chromatography (eluent: 99% CHCl3/MeOH) provided desired product 14a as a pale yellow oil in 80% yield over two steps. Rf = 0.43 (CHCl3/MeOH = 95/5). 1H-NMR (400 MHz, CDCl3): δ 8.81 (s, 1 H), 7.58 (d, J = 8.9 Hz, 1 H), 7.52 (s, 1 H), 7.08 (d, J = 8.8 Hz, 1 H, aromatic), 5.58 (d, J = 3.5 Hz, 1 H), 5.51-5.29 (m, 4 H), 5.22 (dd, J = 10.9, 3.5 Hz, 1 H), 4.99 (s, 1 H), 4.24 (q, J = 6.5 Hz, 1 H), 4.07 (s, 2 H), 3.72-3.65 (m, 6 H), 3.59 (m, 2 H), 3.44 (m, 2 H), 3.20 (m, 2 H), 2.13 (s, 3 H), 2.00 (s, 3 H), 1.97 (s, 3 H), 1.36 (s, 9 H), 1.10 (d, J = 6.5 Hz, 3 H). 13C-NMR (100 MHz, CDCl3): δ 170.4 (C), 170.3 (C), 170.0 (C), 168.1 (C), 155.8 (C), 151.1 (d, J = 4.4 Hz, C), 132.5 (C), 126.2 (d, J = 16.9 Hz, C), 122.0 (CH), 121.3 (d, J = 7.2 Hz, CH), 115.5 (CH), 96.0 (CH), 79.6 (d, J = 165.9 Hz, CH2F), 79.1 (C), 71.0 (CH2), 70.7 (CH), 70.3 (CH2), 70.3 (CH2), 70.0 (CH2), 69.9 (CH2), 69.8 (CH2), 67.8 (CH), 67.6 (CH), 65.4 (CH), 40.1 (CH2), 28.3 (CH3),

15



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20.6 (CH3), 20.5 (CH3), 20.5 (CH3), 15.8 (CH3).

19

Page 16 of 27

F-NMR (376 MHz, CDCl3) δ -214.2 (t, J =

47.8 Hz). IR (neat): 3339, 2918, 2361, 1748, 1708, 1536, 1502, 1369, 1223, 1074 cm-1. HRMS (ESI-quadrupole) calcd for C32H47FN2O14Na for (M + Na)+ 725.2909, found 725.2914. 10-(4-((2,5-Dioxopyrrolidin-1-yl)oxy)-4-oxobutyl)-5,5-difluoro-1,3,7,9-tetramethyl-5H-dip yrrolo[1,2-c:2',1'-f][1,3,2]diazaborinin-4-ium-5-uide

(15).

To

a

solution

of

4-(4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene-8-yl)-butyric acid (135 mg, 0.404 mmol) in 4 mL DMF was added N-hydroxysuccinimide (60 mg, 0.52 mmol), DIEA (67 µL, 0.404 mmol), and EDC (103 mg, 0.54 mmol). The reaction mixture was stirred for 16 h. It was then quenched with 0.2 mL 5% citric acid and stirred for another 10 min. The solvent was then removed under high vacuum. The residual oil was dissolved in 50 mL EtOAc and the solution was washed with 5% citric acid (20 mL x 2), 5% NaHCO3 (20 mL x 2), and brine (20 mL). The organic phase was dried over anhydrous Na2SO4, filtered and concentrated. The desired product 15 was obtained as a dark orange solid in 83% yield after crystallization at 4 oC from CHCl3/hexane. Rf = 0.40 (hexane/EtOAc = 4/6), mp 160 oC (dec). 1H-NMR (400 MHz, CDCl3): δ 6.04 (s, 2 H), 3.13-3.03 (m, 2 H), 2.83 (s, 4 H), 2.78 (t, J = 7.1 Hz, 2 H), 2.49 (s, 6 H), 2.39 (s, 6 H), 2.12-1.97 (m, 2 H).

13

C-NMR (100 MHz, CDCl3): δ 168.9 (C), 167.8 (C), 154.4

(C), 144.0 (C), 140.4 (C), 131.4 (C), 121.9 (CH), 30.9 (CH2), 27.0 (CH2), 26.2 (CH2), 25.6 (CH2), 16.4 (CH3), 14.5 (CH3). 19F-NMR (376 MHz, CDCl3): δ -147.0 (m). IR (KBr): 3454, 2082, 1814, 1784, 1738, 1634, 1551, 1510, 1473, 1409, 1370, 1200, 1159, 1068, 984, 647 cm-1. HRMS (ESI-quadrupole) calcd for C21H24BF2N3NaO4 (M+Na)+ 454.1726, found 454.1735.

16


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General procedure for the preparation of compound 16. The corresponding 14 (138 mg, 0.196 mmol) was dissolved in 2 mL of 20% TFA/CH2Cl2. The solution was stirred for 1 h. The volatiles were concentrated under reduced pressure and the residual was kept under high vacuum for 3 h. To a solutin of the residue in 2 mL of CH2Cl2 was added BODIPY-OSu 15 (88.9 mg, 0.206 mmol) and TEA (164 µL, 1.18 mmol). The reaction mixture was stirred for 6 h at room temperature, diluted with 50 mL of EtOAc, and washed with 5% citric acid (25 mL x 3), 5% NaHCO3 (25 mL x 3), H2O (25 mL x 3) and brine (25 mL). The organic phase was then dried over anhydrous Na2SO4, filtered and concentrated. Purification by silica gel column chromatography (eluent: 98% CHCl3/MeOH) provided the desired product 16 as orange solids in 61−75% yield over two steps. 5,5− −Difluoro− −10− −(1− −((3− −(fluoromethyl)− −4− −(((2S,3S,4R,5R,6S)− −3,4,5− −triacetoxy− −6− −methyl tetrahydro− −2H− −pyran− −2− −yl)oxy)phenyl)amino)− −1,13− −dioxo− −3,6,9− −trioxa− −12− −azahexadecan −16− −yl)− −1,3,7,9− −tetramethyl− −5H− −dipyrrolo[1,2− −c:2',1'− −f][1,3,2]diazaborinin− −4− −ium− −5− −uid e (16a). Orange solid, 61% yield. Rf = 0.63 (CHCl3/MeOH = 9/1), mp 89−91 oC. 1H−NMR (400 MHz, CDCl3): δ 8.71 (s, 1 H), 7.58 (d, J = 8.9 Hz, 1 H), 7.51 (s, 1 H), 7.08 (d, J = 8.8 Hz, 1 H), 6.37 (m, 1 H), 5.98 (s, 2 H), 5.59 (d, J = 3.6 Hz, 1 H), 5.51-5.28 (m, 4 H), 5.23 (dd, J = 10.9, 3.6 Hz, 1 H), 4.23 (q, J = 6.3 Hz, 1 H), 4.07 (s, 2 H), 3.80-3.47 (m, 8 H), 3.46 (m, 2 H), 3.33 (m, 2 H), 2.90 (m, 2 H), 2.43 (s, 6 H), 2.33 (s, 6 H), 2.25 (m, 2 H), 2.14 (s, 3 H), 2.00 (s, 3 H), 1.97 (s, 3 H), 1.85 (m, 2 H), 1.10 (d, J = 6.5 Hz, 3 H). 13C-NMR (100 MHz, CDCl3): δ 171.7 (C), 170.4 (C), 170.3 (C), 170.0 (C), 168.2 (C), 153.8 (C), 151.1 (d, J = 4.3 Hz, C), 145.4 (C), 140.5 (C),

17



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132.4 (C), 131.3 (C), 126.3 (d, J = 16.7 Hz, C), 121.9 (d, J = 3.0 Hz, CH), 121.6 (CH), 121.1 (d, J = 7.6 Hz, CH), 115.6 (CH), 96.0 (CH), 79.6 (d, J = 165.7 Hz, CH2F), 70.7 (CH2), 70.6 (CH), 70.4 (CH2), 70.2 (CH2), 70.2 (CH2), 69.8 (CH2), 69.7 (CH2), 67.8 (CH), 67.6 (CH), 65.5 (CH), 39.1 (CH2), 35.9 (CH2), 27.4 (CH2), 27.3 (CH2), 20.6 (CH3), 20.5 (CH3), 20.5 (CH3), 16.1 (CH3), 15.7 (CH3), 14.3 (CH3). 19F-NMR (376 MHz, CDCl3): δ -147.3 (m), -214.1 (t, J = 47.6 Hz). IR (KBr): 3327, 2923, 1748, 1665, 1550, 1509, 1203 cm-1. HRMS (ESI-quadrupole) calcd for C44H58BF3N4NaO13 (M+Na)+ 941.3943, found 941.3967. 10− −(1− −((3− −(Difluoromethyl)− −4− −(((2S,3S,4R,5R,6S)− −3,4,5− −triacetoxy− −6− −methyltetrahydro −2H− −pyran− −2− −yl)oxy)phenyl)amino)− −1,13− −dioxo− −3,6,9− −trioxa− −12− −azahexadecan− −16− −yl)− −5, 5− −difluoro− −1,3,7,9− −tetramethyl− −5H− −dipyrrolo[1,2− −c:2',1'− −f][1,3,2]diazaborinin− −4− −ium− −5− − uide (16b). Orange solid, 75% yield. Rf = 0.45 (CHCl3/MeOH = 9/1), mp 102−104oC. 1H-NMR (400 MHz, CDCl3): δ 8.79 (s, 1 H), 7.84 (dd, J = 9.0, 2.2 Hz, 1 H), 7.60 (d, J = 2.2 Hz, 1 H), 7.17 (d, J = 9.0 Hz, 1 Hc), 6.96 (t, J = 55.4 Hz, 1 H), 6.24 (t, J = 5.4 Hz, 1 H), 6.00 (s, 2 H), 5.62 (d, J = 3.7 Hz, 1 H), 5.45 (dd, J = 10.9, 3.3 Hz, 1 H), 5.35 (m, 1 H), 5.24 (dd, J = 10.9, 3.7 Hz, 1 H), 4.25 (q, J = 6.5 Hz, 1 H), 4.10 (s, 2 H), 3.72-3.59 (m, 8 H), 3.49 (m, 2 H), 3.36 (m, 2 H), 2.95 (m, 2 H), 2.47 (s, 6 H), 2.37 (s, 6 H), 2.30 (m, 2 H), 2.16 (s, 3 H) 2.02 (s, 3 H), 2.00 (s, 3 H), 1.91 (m, 2 H), 1.13 (d, J = 6.5 Hz, 3 H). 13C-NMR (100 MHz, CDCl3): δ 171.7 (C), 170.4 (C), 170.4 (C), 170.0 (C), 168.4 (C), 153.9 (C), 151.3 (C), 145.4 (C), 140.5 (C), 132.7 (C), 131.4 (C), 124.2 (C), 124.0 (CH), 121.7 (CH), 117.9 (CH), 116.3 (CH), 109.8 (t, J = 118.7 Hz, CH), 96.5 (CH), 70.9 (CH2), 70.6 (CH), 70.4 (CH2), 70.3 (CH2), 70.3 (CH2), 69.8 (CH2), 69.8 (CH2), 67.8 (CH), 67.7

18


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Page 19 of 27

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(CH), 65.8 (CH), 39.2 (CH2), 36.0 (CH2), 27.5 (CH2), 27.4 (CH2), 20.6 (CH3), 20.6 (CH3), 20.5 (CH3), 16.3 (CH3), 15.8 (CH3), 14.4 (CH3).

19

F-NMR (376 MHz, CDCl3): δ -114.0 (dd, J =

300.7, 55.5 Hz), -117.6 (dd, J = 300.8, 55.4 Hz ), -147.5 (m). IR (KBr): 3341, 2926, 1749, 1550, 1509, 1224 cm-1. HRMS (ESI-quadrupole) calcd for C44H57BF4N4NaO13 (M+Na)+ 959.3849, found 959.3841. General procedure for the preparation of compound 5. To a solution of the corresponding 16 (90.0 mg, 0.0980 mmol) in 1 mL of MeOH/CH2Cl2 (2/1) was added Na2CO3 (41.5 mg, 0.392 mmol). The reaction mixture was stirred for 4 h, diluted with 50 mL of EtOAc, and washed with 5% citric acid (25 mL x 3), H2O (25 mL x 2) and brine (25 mL). The organic phase was dried over anhydrous Na2SO4, filtered and concentrated. The residue was triturated with hexane, and recrystallized in ether/MeOH to provide the desired products 5a and 5b. 5,5− −Difluoro− −10− −(1− −((3− −(fluoromethyl)− −4− −(((2S,3S,4R,5S,6S)− −3,4,5− −trihydroxy− −6− −methy ltetrahydro− −2H− −pyran− −2− −yl)oxy)phenyl)amino)− −1,13− −dioxo− −3,6,9− −trioxa− −12− −azahexadeca n− −16− −yl)− −1,3,7,9− −tetramethyl− −5H− −dipyrrolo[1,2− −c:2',1'− −f][1,3,2]diazaborinin− −4− −ium− −5− −ui de (5a). Orange solid, 92% yield. Rf = 0.40 (CHCl3/MeOH = 85/15), mp 103−104 oC. 1H−NMR (400 MHz, CD3OD): δ 7.61 (s, 1 H), 7.54 (d, J = 8.7 Hz, 1 H), 7.15 (d, J = 8.7 Hz, 1 H), 6.06 (s, 2 H), 5.55 (dd, J = 48.0, 11.3 Hz, 1 H), 5.45 (d, J = 2.1 Hz, 1 H), 5.42 (dd, J = 47.8, 11.3 Hz, 1 H), 4.06 (s, 2 H), 3.99 (q, J = 6.7 Hz, 1 H), 3.93 (m, 2 H), 3.71 (s, 1 H), 3.66−3.60 (m, 8 H), 3.50 (m, 2 H), 3.34 (m, 2 H), 2.87 (m, 2 H), 2.42 (s, 6 H), 2.33 (s, 6 H), 2.30 (m, 2 H), 1.80 (m, 2 H), 1.15 (d, J = 6.6 Hz, 3 H). 13C−NMR (100 MHz, CD3OD): δ 174.8 (C), 170.7 (C), 155.0 (C),

19



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Page 20 of 27

152.9 (d, J = 4.3 Hz, C), 147.1 (C), 142.4 (C), 133.2 (C), 132.5 (C), 127.9 (d, J = 16.6 Hz, C), 123.3 (d, J = 2.6 Hz, CH), 122.7 (CH), 122.5 (d, J = 8.1 Hz, CH), 116.5 (CH), 99.7 (CH), 81.2 (d, J = 163.8 Hz, CH2F), 73.4 (CH), 71.9 (CH2), 71.6 (CH2), 71.5 (CH), 71.4 (CH2), 71.4 (CH2), 71.1 (CH2), 70.4 (CH2), 69.6 (CH), 68.8 (CH), 40.4 (CH2), 36.9 (CH2), 28.9 (CH2), 28.5 (CH2), 16.7 (CH3), 16.5 (CH3), 14.5 (CH3). 19F−NMR (CD3OD, 376 MHz): δ −147.6 (m), −216.7 (t, J = 47.7 Hz). IR (KBr): 3450, 1658, 1549, 1502 cm−1. HRMS (ESI-quadrupole) calcd for C38H52BF3N4NaO10 (M+Na)+ 815.3626, found 815.3621. 10− −(1− −((3− −(Difluoromethyl)− −4− −(((2S,3S,4R,5S,6S)− −3,4,5− −trihydroxy− −6− −methyltetrahydro −2H− −pyran− −2− −yl)oxy)phenyl)amino)− −1,13− −dioxo− −3,6,9− −trioxa− −12− −azahexadecan− −16− −yl)− −5, 5− −difluoro− −1,3,7,9− −tetramethyl− −5H− −dipyrrolo[1,2− −c:2',1'− −f][1,3,2]diazaborinin− −4− −ium− −5− − uide (5b). Orange solid, 92% yield. Rf = 0.19 (CHCl3/MeOH = 9/1), melting point 97−99 oC. 1

H−NMR (400 MHz, CD3OD): δ 8.08 (s, 1 H), 7.82 (s, 1 H), 7.67 (d, J = 8.6 Hz, 1 H), 7.24 (d, J

= 8.9 Hz, 1 H), 7.16 (t, J = 55.4 Hz, 1 H), 6.08 (s, 2 H), 5.48 (s, 1 H), 4.08 (s, 2 H), 3.98 (q, J = 6.6 Hz, 1 H), 3.94 (m, 2 H), 3.73 (s, 1 H), 3.67−3.63 (m, 8 H), 3.52 (m, 2 H), 3.34 (m, 2 H), 2.94 (m, 2 H), 2.42 (s, 6 H), 2.38 (s, 6 H), 2.32 (m, 2 H), 1.86 (m, 2 H), 1.17 (d, J = 6.3 Hz, 3 H). 13

C−NMR (100 MHz, CD3OD): δ 175.0 (d, J = 8.6 Hz, C), 170.9 (C), 155.1 (C), 153.0 (d, J = 4.3

Hz, C), 147.1 (C), 142.4 (C), 133.4 (C), 132.6 (C), 125.5 (C), 125.3 (CH), 122.7 (CH), 119.5 (CH), 117.0 (CH), 111.7 (t, J = 117.8 Hz, CH), 100.0 (CH), 73.3 (CH), 71.9 (CH2), 71.6 (CH2), 71.4 (CH2), 71.4 (CH), 71.1 (CH2), 70.4 (CH2), 69.5 (CH), 69.0 (CH), 40.6 (CH2), 40.4 (CH2), 37.0 (CH2), 29.1 (CH2), 28.5 (CH2), 16.6 (CH3), 16.5 (CH3), 14.5 (CH3).

20


19

F−NMR (376 MHz,

Page 21 of 27

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CD3OD): δ −112.3 (dd, J = 300.3, 55.8 Hz), −122.9 (dd, J = 300.3, 54.9 Hz), −147.9 (m). IR (KBr): 3315, 2922, 1662, 1550, 1501, 1202, 1084 cm−1. HRMS (ESI-quadrupole) calcd for C38H51BF4N4NaO10 (M+Na)+ 833.3532, found 833.3533. (2-Difluoromethyl-4-nitro-phenyl)-tetra-O-acetyl-α-L-fucopyranoside

(17).

To

an

ice-cooled solution of compound 9 (100 mg, 0.228 mmol) in 1 mL of anhydrous CH2Cl2 was added a solution of DAST (0.42 mL, 0.342 mmol) in 1 mL of anhydrous CH2Cl2. The reaction mixture was allowed to warm to room temperature, and stirred for another 24 h under N2. It was quenched by adding a small amount of silica gel and 1 mL MeOH, filtered and concentrated under reduced pressure. Purification by silica gel column chromatography (eluent: 80% hexane/EtOAc) provided the desired fluorinated product 17 as a colorless solid in 97% yield. Rf = 0.50 (hexane/EtOAc = 1/1), mp 185−187 oC. 1H-NMR (400 MHz, CDCl3): δ 8.46 (d, J = 2.7 Hz, 1 H), 8.32 (dd, J = 9.2, 2.7 Hz, 1 H), 7.34 (d, J = 9.2 Hz, 1 H), 6.95 (t, J = 54.8 Hz, 1 H), 5.85 (d, J = 3.7 Hz, 1 H), 5.45 (dd, J = 10.9, 3.2 Hz, 1 H), 5.38 (d, J = 3.2 Hz, 1 H), 5.28 (dd, J = 10.9, 3.7 Hz, 1 H), 4.19 (q, J = 6.5 Hz, 1 H), 2.19 (s, 3 H), 2.03 (s, 3 H), 2.02 (s, 3 H), 1.14 (d, J = 6.5 Hz, 3 H). 13C-NMR (100 MHz, CDCl3): δ 170.4 (C=O), 170.3 (C=O), 169.9 (C=O), 158.9 (C), 142.6 (C), 128.0 (CH), 124.6 (t, J = 23.5 Hz, C), 122.7 (CH), 115.1 (CH), 110.1 (t, J = 237.5 Hz, -CHF2), 96.0 (CH), 70.3 (CH), 67.6 (CH), 67.3 (CH), 66.6 (CH), 20.6 (CH3), 20.5 (CH3), 20.5 (CH3), 15.8 (CH3). 19F-NMR (376 MHz, CDCl3): δ -116.9 (dd, J = 302.5, 54.9 Hz), -118.5 (dd, J = 324.0, 60.0 Hz). IR (KBr): 1747, 1614, 1516, 1474, 1369, 1348, 1214, 1074, 1032 cm−1. FAB

21



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MS m/z (%) 273.1 (100), 484.2 (M+Na+, 22). HRMS (ESI-quadrupole) calcd for C20H22F2NO12 (M+FA-H)- 506.1110, found 506.1083. (2S,3S,4R,5R,6S)− −2− −(2− −(Difluoromethyl)− −4− −(2,2− −dimethyl− −4− −oxo− −3,8,11,14− −tetraoxa− −5− − azahexadecanamido)phenoxy)− −6− −methyltetrahydro− −2H− −pyran− −3,4,5− −triyl triacetate (14b). To a solution of compound 17 (93.5 mg, 0.203 mmol) in 2 mL of EtOAc/EtOH (1/1) was added 20% Pd/C catalyst (20 mg). The reaction mixture was purged and filled with H2, stirred for 2 h at rt. It was then filtered through a fritted funnel dry packed with Celite and concentrated under reduced pressure. The residue obtained was dissolved in 1 mL of CH2Cl2 and the solution was added compound 13 (71.8 mg, 0.213 mmol), HOBt (13.7 mg, 0.101 mmol), DIEA (84 µL, 0.51 mmol) and EDC (77.7 mg, 0.405 mmol). The reaction mixture was stirred for 16 h, diluted with 50 mL of EtOAc, and washed with 5% citric acid (25 mL x 3), 5% NaHCO3 (25 mL x 3), H2O (25 mL x 3) and brine (25 mL). The organic phase was dried over anhydrous Na2SO4, filtered and concentrated. Purification by silica gel column chromatography (eluent: 98% CHCl3/MeOH) provided desired product 14b as a pale yellow oil in 81% yield over two steps. Rf = 0.50 (CHCl3/MeOH = 95/5). 1H-NMR (400 MHz, CDCl3): δ 8.91 (s, 1 H), 7.83 (dd, J = 9.0, 2.2 Hz, 1 H), 7.61 (d, J = 2.2 Hz, 1 H), 7.16 (d, J = 9.0 Hz, 1 H), 6.95 (t, J = 55.4 Hz, 1 H), 5.62 (d, J = 3.6 Hz, 1 H), 5.45 (dd, J = 10.9, 3.3 Hz, 1 H), 5.35 (m, 1 H), 5.24 (dd, J = 10.9, 3.7 Hz, 1 H), 4.96 (s, 1 H), 4.27 (q, J = 6.5 Hz, 1 H), 4.09 (s, 2 H), 3.74-3.60 (m, 8 H), 3.47 (m, 2 H), 3.22 (m, 2 H), 2.16 (s, 3 H), 2.02 (s, 3 H), 1.99 (s, 3 H), 1.39 (s, 9 H), 1.14 (d, J = 6.5 Hz, 3 H). 13C-NMR (100 MHz, CDCl3): δ 170.4 (C), 170.3 (C), 169.9 (C), 168.3 (C), 155.8 (C), 151.1 (C), 132.8 (C),

22


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124.1 (t, J = 22.6 Hz, C), 124.1 (CH), 118.1 (CH), 116.1 (CH), 111.0 (t, J = 236.7 Hz, CH), 96.3 (CH), 79.1 (C), 71.1 (CH2), 70.6 (CH), 70.3 (CH2), 70.3 (CH2), 70.1 (CH2), 69.9 (CH2), 69.8 (CH2), 67.8 (CH), 67.6 (CH), 65.7 (CH), 40.2 (CH2), 28.3 (CH3), 20.6 (CH3), 20.5 (CH3), 20.5 (CH3), 15.8 (CH3). 19F-NMR (376 MHz, CDCl3): δ -114.2 (dd, J = 301.1, 55.6 Hz), -117.6 (dd, J = 301.1, 55.3 Hz). IR (neat): 3341, 2932, 1750, 1712, 1538, 1504, 1370, 1247 cm-1. HRMS (ESI-quadrupole) calcd for C32H45F2N2O14 (M-H)- 719.2839, found 719.2850.

ACKNOWLEDGMENT. of

Science

and

This research was supported by Academia Sinica and the Ministry

Technology

(MOST-102-2113-M-002-004-MY3

to

L.-C.L.;

MOST-100-2113-M-001-021-MY3 and MOST-102-2923-M-001-001-MY3 to C.-H.L.).

Supporting Information Available: 1

H/13C NMR spectra for compounds 5, 8-17 are included. Conditions and data for the slot blot

and confocal imaging experiments are also included. This material is available free of charge via the Internet at http://pubs.acs.org.

23



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